Heating, ventilating, and air conditioning (HVAC), sometimes referred to as climate control, involves closely regulating humidity and temperature in order to maintain a comfortable, safe and healthy environment inside a building. HVAC has been described in detail in “Simplified design of HVAC systems” (William Bobenhausen—1994—Technology & Engineering). HVAC system settings are controlled by a thermostat inside a building and typically include a controller device that adjusts the temperature settings for different times of day and different days of the week. The controller device acts as a programmable interface with users of the building. Over many years there have been many improvements in the components of HVAC systems including higher efficiency systems and improved system controllers. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) fulfills its mission of advancing HVAC and refrigeration to serve humanity and promote a sustainable world through research, standards writing, publishing and continuing education. ASHRAE have suggested standards (e.g., ASHRAE Standard 62.2) for ventilation and acceptable indoor air quality that requires fresh air to be ventilated into a house or building to at least a minimum level. To provide an informative background of information, ASHRAE Standard 62.2 and other information about HVAC provided by ASHRAE are hereby incorporated by reference.
Existing HVAC systems are shown in FIG. 1 which provides a schematic of a building that includes an HVAC system that includes heating and cooling devices, heat exchangers, fans, ductwork and dampers. Said system is controlled by a controller designed to determine switch-point on/off settings for elements of the HVAC system. The controller achieves a comfortable indoor setting by determining timing of switch points during continuous monitoring the indoor environment from one or multiple sensors that includes for example thermostats and humidistats. One significant drawback with such HVAC systems is that they do not comply with ASHRAE Standard 62.2 because they typically do not provide any outside ventilation capability.
In recent years as a result of improvements in building engineering, fresh air impact has declined as buildings have become more airtight. Fewer drafts means improved heating and cooling efficiency. Importantly it has also meant that indoor air can be stale and some would argue not so healthful. To that end improvements in HVAC have been sought that involve finding ways to sample outside air to provide ventilation. Some solutions use heat-exchangers to conserve the energy in a building. Improved HVAC systems are shown in FIG. 2 which provides a schematic of a building that includes an HVAC system similar to that shown in FIG. 1 but with the additional capability of fresh air ventilation using a selectively operable damper and fan. This type of system is present in some modern HVAC systems (e.g., Aprilaire Model 8126 Ventilation Control System, or Honeywell Fresh Air Ventilation System Power-Open Spring-Closed Damper & W8150A Control) and is also controlled by a controller. Such controllers typically prevent the system from sampling outside air when temperatures are below or above a certain limit. One significant drawback with currently available ventilation with HVAC is too little fresh air ventilation or random timing of control of fresh-air sampling that causes poor energy efficiency in the HVAC system. Some improvements, such as U.S. Pat. No. 7,044,397, are designed to improve fresh air ventilation have been made by determining a fraction of time that the fresh air intake must be open during anticipated future system calls of the HVAC system to meet a desired ventilation threshold. Another improvement such as U.S. Pat. No. 6,095,426 involves feedback and feedforward control strategies and a method of controlling such apparatus for improved performance. Whilst these improvements in ventilation capability are built into the HVAC system their control is notably not integrated with the HVAC controller.
Existing literature clearly demonstrates that using outside ventilation as part of a mixed-mode cooling system can reduce building operating costs and carbon emissions (e.g., see ASHRAE Transactions: 2006; 112: 281-3571). Typically such cooling methods are built on individual trial and error principles and do not rely on optimized mathematical algorithms that account for outside conditions and inside occupant comfort. Such buildings are often controlled by individual occupants opening windows and doors to permit outside ventilation. Whilst this approach is very effective it does not adapt quickly to outside conditions and does not function without active occupant participation and is not inherently optimized to minimize costs. There is clearly a need for a more adaptive automated approach that might be integrated with existing HVAC capability. A recent publication by Spindler and Norford (2008) describes controlling algorithms for mixed-mode cooling strategies including use of natural ventilation (Naturally ventilated and mixed-mode buildings—Part I: Thermal modeling. Building and Environment, in press (doi: 10.1016/j.buildenv.2008.05.019)). A second publication by Spindler and Norford describes ways to optimize the controlling algorithms for mixed mode cooling (Naturally ventilated and mixed-mode buildings—Part II: Optimal control. Building and Environment In Press, (doi: 10.1016/j.buildenv.2008.05.018)). Important overall conclusions from these studies are that HVAC control algorithms can be built using linear thermal modeling and can be optimized for use in buildings. What is apparent from the literature as well as in fact from a review of existing HVAC control equipment, is the surprising lack of automated integration of mixed-mode heating and cooling using a combination of ventilation and HVAC.
The presently claimed invention (referred to hereinafter as a “Smart Stat Controller” or “Smart Thermostat” or alternatively “Smart-Stat”) overcomes the random timing and inefficient use of fresh air ventilation by incorporating a novel control system. FIG. 3 provides a schematic of a building that includes an HVAC system similar to that shown in FIG. 2 but with the additional capability of incorporating the present invention. FIG. 4 provides a schematic of a typical controller, whilst FIG. 5 provides a schematic of the present invention's programmable controller or smart thermostat (Smart-Stat). FIG. 6 provides a second schematic of the present invention's programmable controller configured with an existing typical thermostatic controller. The Smart Thermostat system is designed to optimize the timing of use of fresh air based on current outside conditions in combination with data from weather forecasts. Specifically the Smart Thermostat controller controls air-flow and HVAC in buildings by using mathematical algorithms that monitors regional weather forecasts in combination with current outside air monitoring. The present invention saves energy and reduces the carbon footprint of heating and cooling by achieving optimal timing of HVAC combined with use of ambient air ventilation as an alternative to heating and cooling. In short, the Smart-Stat controller uses outside ventilation to achieve the desired result of providing a comfortable inside air temperature and quality against user-programmable set-points.
Previously described improvements in HVAC utilize counter-flow systems that radiate heat from incoming and outgoing air. In addition, some of the said improved HVAC systems include temperature sensors for the inside and outside air that are used to set dampers flow rate in order to conserve energy. Thus it can be envisioned one aspect of the concept of the present Smart-Stat invention can be seen within these improvements to HVAC. Specifically, the existing HVAC improvements include monitoring inside and outside temperatures in order to control energy flow between incoming and outgoing air. Some of these systems integrate this control with weather information but importantly, the improved indoor ventilation is only a fraction of the air flow. Furthermore, unlike the present invention, the improved HVAC systems sample outside air with the purpose of improved air quality and the outside air is heated or cooled in just the same way as indoor air, all under the control of a typical thermostatic controller. Importantly the present invention uses the existing HVAC system to circulate air and bring-in outside air to over-ride the use of heating and cooling as used in the typical thermostat controller and improved HVAC systems. Specifically in none of the HVAC improvements is there a system for using the outside air as an alternative source of heating or cooling with the specific goal of reducing costs and reducing the carbon footprint of HVAC systems.
Another existing technology that shares similarities with the present invention is the use of whole house ventilation fans or window fans to cool or warm a house using outside air. Here, the purpose is similar to that described by the present invention: namely energy saving using outside air. Sometimes called “Whole House Ventilation” or “Whole House Fans”, these systems provide a fan often mounted in the ceiling that vents air into the attic where the air is lost passively or expelled using another fan in the roof space. These systems are often controlled using a switch, activated by a user and requires that said user has opened windows within the home. Sometimes the fans are activated by the user and rely upon opened wall ventilation panels to allow balanced air flow. Sometimes the fans are activated by temperature sensors. Importantly, in none of these examples is there an attempt to integrate or automate the Whole House Ventilation with an existing HVAC nor is there any integration with the buildings HVAC Control system or control software. Thus the user has to switch them on manually and manually switch off the HVAC system. More importantly the Whole House System does not bring together a monitoring system for inside and outside conditions with time and additionally does not integrate this with weather data monitoring to predict an optimal use of outside air. Thus the present invention overcomes the limitations of the existing systems of HVAC by bringing together such data into logical algorithms that make optimal automated use of outside weather conditions. Initially we modeled the cost saving potential using spreadsheets based on actual temperature data downloaded from the Iowa State University μg Climate 2005, 2006, 2007—Iowa Environmental Mesonet. Significant annual cost savings were possible during certain months (April through October) when temperatures were not extreme.
Yet another existing technology that shares similarities with the present invention is the use of on-line weather data to monitor local weather forecasts and take proactive steps in system operation and control. Here, the purpose is similar to that described by the present invention: namely using weather forecasting information to make decisions on controlling the HVAC system. However, the present invention uses the weather information to call on outside ventilation in place of HVAC, whereas the existing technologies proactively change the HVAC settings in days preceding weather events by increasing or decreasing cooling or heating in order to place less demand on the system on the day of the weather event. Thus the present invention overcomes the limitations of the existing technological advances in systems of HVAC control by bringing together such data into logical algorithms that monitors outside weather conditions and terminates calls for HVAC, redirecting this into calls for fresh air ventilation by reacting to outside weather conditions.
Smart-Stat can be linked with home computer monitoring and control systems and computer software systems by using any kind of suitable interface. For example, industry-standard RS-232/RS-485 protocol, or X10-Control or Z-Wave control. X10 is an international and open industry standard for communication among electronic devices used for home automation, also known as domotics. X10 primarily uses power line wiring for signaling and control, where the signals involve brief radio frequency bursts representing digital information. A wireless radio based protocol transport can also be also defined. Z-Wave is a wireless communications standard designed for home automation, such as remote control applications in residential and light commercial environments.
Smart-Stat uses the National Digital Forecast Database (NDFD) Extensible Markup Language (XML) as a service, accessing local weather data from the National Weather Service's (NWS) digital forecast database. This service, which is defined in a Service Description Document, provides the ability to request NDFD data over the internet and receive the information back in an XML format. The request/response process is made possible by the NDFD XML Simple Object Access Protocol (SOAP) server. The first step to using the web service is to create a SOAP client. The client creates and sends the SOAP request to the server. The request sent by the client then invokes one of the server functions. There are currently nine functions available including: NDFDgen(), NDFDgenLatLonList(), LatLonListSubgrid(), LatLonListLine(), LatLonListZipCode(), LatLonListSquare(), CornerPoints(), NDFDgenByDay(), and NDFDgenByDayLatLonList(). Said weather data will include a time-based forecast of temperature and relative humidity as well as hours of sunshine or cloud-cover. Upon receiving said weather data, the present invention monitors local weather forecasts for the coming days ahead and integrates this information with current inside and outside temperatures. Computational algorithms based on the local forecasts and local data are then used by Smart-Stat to make logical choices that control the HVAC system and determine appropriate use of fresh air ventilation. The system is designed not to operate ventilation if the outside air is below 40° F. or above 100° F. and if the relative humidity is above 60%.
The present invention is also able to use its outside/inside/weather monitoring capability to compute models of heat-loss and heat-gain for the local building in which it is placed. Such models represent coefficients of heat loss/gain in different environmental conditions and enable more sophisticated algorithms to be computed that will improve the ability of the control system to determine optimal set-points for the HVAC system and determine optimal use of fresh air ventilation. Thus the system learns over time and adjusts set-points accordingly. Another aspect of this monitoring system is its ability to output heat-transfer information to the local user as well as local service/installation companies. Such data output would allow the local users to recognize differences between houses in terms of heat transfer, and enable a data-driven recommendation for improvements in building insulation. The outcome would be improvements in the overall energy consumption of buildings in relation to heating and cooling requirements. Such improvements would have an impact on local and regional carbon footprints regarding energy utilization.
In light of these developments in the art, a number of patent and other documents are referenced herein which relate to efforts to modify HVAC and to achieve improvements in energy efficiency. These documents are hereby incorporated by reference.
Thus, for example U.S. Pat. No. 7,044,397 describes improved fresh air ventilation by determining a fraction of time that the fresh air intake must be open during anticipated future system calls of the HVAC system to meet a desired ventilation threshold. Another improvement such as U.S. Pat. No. 6,095,426 describes feedback and feedforward control strategies and a method of controlling such apparatus for improved performance.
U.S. Pat. No. 5,746,653 describes an apparatus mounted in for example an attic that can distribute and collect air where a fan draws air from a perforated elongated tube and vents the air as needed in order to provide cooling or heating in a building.
U.S. Pat. No. 5,761,083 describes an Energy Management and Home Automation system that senses the mode of occupancy of the building. Thus control is different when occupied or unoccupied and heating and cooling based is switched appropriately.
U.S. Pat. No. 6,095,426 involves feedback and feedforward control strategies and a method of controlling such apparatus for improved performance.
U.S. Pat. Nos. 6,756,998 and 6,912,429 detects building occupancy status using motion sensor devices interfaced with the controller unit. The system even learns from data inputs and builds an occupancy pattern for each room.
U.S. Pat. No. 6,766,651 describes use of humidity control and aromas and even pesticidal, bacteriacidal, fungicidal or sporacidal agents can be introduced into the airflow to enhance HVAC.
U.S. Pat. No. 7,044,397 describes use of fresh air ventilation wherein a fraction of time is determined for fresh air intake opening during anticipated future system calls of the HVAC system to meet a desired ventilation threshold.
U.S. Pat. No. 7,343,226 describes a system and method of controlling an HVAC system that incorporates outside temperature monitoring and is linked to demand and consumption rate from the distribution network.
U.S. Pat. No. 7,434,742 describes a thermostat having a microprocessor and network interface to obtain user-specified information from a remote service provider plus a display device responsive to the microprocessor for displaying user-specified information received via the network controller from the remote service provider.
Patent WO/2007/094774 describes a method and apparatus for maintaining an acceptable level of outside air exchange rate in a structure. The natural ventilation rate is determined as a function of the outdoor air temperature, and the amount of mechanically induced ventilation that is used to supplement the natural air ventilation is controlled such that the sum of the natural occurring ventilation and the mechanically induced ventilation is maintained by a substantially constant predetermined level.
Patent WO/2007/117245 describes a controller for an HVAC & R system is provided with the Internet connection to weather forecast information in order to determine proactive steps that increase heating or decrease cooling, or alternatively decrease heating or increase cooling, prior to changes in weather beginning to occur. The patent also describes using the proactive monitoring system to control fresh air circulation rate.
HVAC engineers continue to research ways to optimize the operation of heating and cooling systems, however despite various publications, practical applications are not apparent. For example, although Zaheer-uddin and Zheng describe optimal control of HVAC (Energy Conversion and Management (2000) 41, 49-60), whilst Chen describes adaptive predictive control for heating applications (Energy and Buildings (2002) 34, 45-51) and more recently, He, Cai and Li describe use of multiple fuzzy model-based temperature predictive control systems (Information Sciences (2005) 169, 155-174) none of these publications describe practical examples of improved control systems.
As can be seen from the foregoing review of the art, there is intense interest in improving HVAC and its impact on energy utilization and carbon footprint. There exist problems in various aspects of the known technologies, from using more efficient heat exchangers to improved monitoring and the like. Accordingly, there remains a need in the art for novel methods and compositions which provide improvements in energy utilization and carbon footprint control. The present invention provides a valuable additional set of novel methods and control systems which meet these needs while placing a minimal burden on HVAC systems needing modification according to this technology.